Touch screen

Abstract

An touch screen of the voltage-divider type is provided which includes two substrates spaced apart from each other by a gap, each substrate including a region formed of conductive material formed in overlapping relationship to each other. A pair of strips formed from a resistive material is coupled to opposed edges of each conductive region such that the resistance strips of the first substrate extend in a substantially perpendicular direction to the resistance strips of said the second substrate. A circuit is provided which applies a first reference voltage across the resistance strips of the first substrate, and subsequently applies a second reference voltage across the resistance strips of the second substrate.

What is claimed is: 
     
       1. A touch screen, comprising: a first and second substrate, said first substrate being spaced apart from said second substrate by a gap,   a pair of regions formed of conductive material formed on said first and second substrates respectively, in overlapping relationship,   a pair of strips formed from a resistive material coupled to opposed edges of each conductive region such that said resistance strips of said first substrate extend in a substantially perpendicular direction to said resistance strips of said second substrate,   a circuit which applies a first reference voltage across the resistance strips of the first substrate, and subsequently applies a second reference voltage across the resistance strips of the second substrate, said circuit being structured and arranged to calculate an X coordinate based on a voltage drop across each resistance strip of said first substrate independent of a voltage drop across the other resistance strip of said first substrate and being structured and arranged to calculate a Y coordinate based on a voltage drop across each resistance strip of said second substrate independent of a voltage drop across the other resistance strip of said second substrate.   
     
     
       2. The touch screen according to claim 1, wherein the first reference voltage equals the second reference voltage. 
     
     
       3. The touch screen according to claim 1, wherein said pair of regions formed of conductive material comprise a plurality of conductive strips coupled at their ends to said resistance strips of their respective substrates. 
     
     
       4. The touch screen according to claim 1, wherein said conductive region of said first substrate faces said conductive region of said second substrate. 
     
     
       5. The touch screen according to claim 1, wherein said circuit includes digital-to-analog circuitry for applying said first and second reference voltages to said resistance strips of said first and second substrates respectively. 
     
     
       6. The touch screen according to claim 5, wherein said digital-to-analog circuitry continuously toggles said applied reference voltages between said resistance strips of said first and second substrates. 
     
     
       7. The touch screen according, to claim 6, wherein said digital-to-analog circuitry toggles said applied voltage approximately every 5 microseconds. 
     
     
       8. The touch screen according to claim 1, wherein said conductive strips are formed from a material chosen from the group consisting of indium tin-oxide and conductive silver ink. 
     
     
       9. The touch screen according to claim 1, wherein said first conduction region and said second conduction region are formed from graphite. 
     
     
       10. The touch screen according to claim 1, wherein said first substrate and said second substrate are about 0.007 inches thick. 
     
     
       11. The touch screen according to claim 1, wherein each resistance strip of said first and second substrates have a resistance ranging from about 100 ohms to about 10,000 ohms. 
     
     
       12. The touch screen according to claim 1, further comprising a circuit which measures a voltage of said second substrate when said first reference voltage is applied across said resistance strips of said first substrate, and measures a voltage of said first substrate when said second reference voltage is applied across said resistance strips of said second substrate. 
     
     
       13. A touch screen, comprising: a first rectangular conductive region having an active area of a negligible resistance adapted to be touched and an inactive area situated on the perimeter of said active area, said first conductive region being coupled to a first pair of resistance strips, each resistance strip of said first pair being arranged along a vertical edge of said first conductive region in said inactive area,   a second rectangular conductive region having an active area of a negligible resistance and an inactive area situated on the perimeter of said active area, said second conductive region situated in a plane parallel to said first conductive region, said second conductive region being coupled to a second pair of resistance strips, each resistance strip of said second pair being arranged along a horizontal edge of said second conductive region in said inactive area, and   a circuit which applies a first reference voltage across said resistance strips of said first substrate, and subsequently applies a second reference voltage across said resistance strips of said second substrate, said circuit being structured and arranged to calculate an X coordinate based on a voltage drop across each resistance strip of said first substrate independent of a voltage drop across the other resistance strip of said first substrate and being structured and arranged to calculate a Y coordinate based on a voltage drop across each resistance strip of said second substrate independent of a voltage drop across the other resistance strip of said second substrate.